JP4811672B2 - Soluble stopper alloy and fusible stopper - Google Patents

Description

  The present invention relates to a fusible plug alloy that operates as a protection mechanism of a refrigeration apparatus, and more particularly to a fusible plug alloy that operates at 66 to 70 ° C. and a fusible plug using the fusible plug alloy.

  In a large refrigeration apparatus, when the pressure inside the refrigeration apparatus abnormally increases or the temperature of the refrigerant rises, not only the refrigerator itself is damaged, but also high pressure gas is ejected and the surroundings may be destroyed. Large refrigeration equipment is obliged to make the pressure of refrigerant gas in the refrigeration equipment safe as a mechanism to prevent breakage and destruction of the refrigerator (Article 7 Paragraph 1 No. 8 of the Ministry of Economy, Trade and Industry) In general, a safety device such as a fusible stopper is provided. The safety device of the refrigeration apparatus is designed for each company depending on the refrigerant used. Conventionally, the refrigerant used in the refrigeration apparatus has been most frequently used as CFC (Chloro Fluoro-Carbons) refrigerant. However, the CFC-based refrigerant has a problem that it is photolyzed by the ultraviolet rays of sunlight in the stratosphere to generate active chlorine, and the ozone layer is destroyed by this active chlorine. It was. For this reason, HCFC (Hydro, Chloro, Fluoro-Carbons) refrigerants, which are alternative chlorofluorocarbons, are now being replaced, and HFC (Hydro, Fluoro-Carbons) refrigerants with a smaller ozone layer depletion coefficient also appear. The refrigerant used for refrigerators is also changing.

  The fusible stopper used in the refrigeration apparatus needs to be designed according to the refrigerant used. In other words, in the refrigeration apparatus, the temperature of the refrigerant used increases as the pressure of the refrigerant used in the refrigeration apparatus rises according to Boyle Charles's law. It is determined. For example, in the case of an air-conditioning refrigeration apparatus in which R22 (HCFC22), which is currently most in demand as an HCFC-based refrigerant, is selected as a refrigeration apparatus refrigerant, the condensation pressure is 1.94 MPa, so the critical temperature of R22 is 96.2 ° C. Thus, the operating temperature of the fusible plug is designed to be about 95-100 ° C.

  Moreover, since the critical temperature of the fusible plug used in the refrigeration apparatus changes depending on the refrigerant, it is necessary to redesign the operating temperature when the refrigerant is switched. R404A, an HFC refrigerant used as an alternative refrigerant with a small ozone layer depletion coefficient, has a condensing pressure of 3061 Kpa and a critical temperature of 71.6 ° C, so the design temperature of the fusible plug must be 66-70 ° C. I must.

  By the way, since a low melting solder alloy is used for the fusible plug used in the refrigeration apparatus, a solder alloy containing Pb and Cd which are harmful substances has been used. When R22 is used as the refrigerant, the design temperature of the fusible plug is 96 ° C, so Sn-52Bi-32Pb (96 ° C eutectic) is used, and when R410a is used as the refrigerant, the fusible plug design Since the temperature is 71 to 75 ° C, a solder alloy such as Sn-50Bi-10Cd-26.7Pb (solid phase temperature 69 ° C, peak temperature 76 ° C, liquid phase temperature 81 ° C) has been used.

In general, the fusible stopper is collected together with the refrigeration apparatus. When the refrigeration apparatus is discarded, it is a matter of course that processing in accordance with the regulations is required. Particularly in recent years, the movement of protecting the global environment has become active, and there is a tendency to eliminate harmful components from parts used in equipment such as refrigeration equipment. In particular, Cd and Pb components are regulated because they adversely affect the human body.

As a fusible stopper alloy that does not contain harmful components such as Cd and Pb, an alloy that uses two or more alloys selected from Sn, Bi, In, Zn, and Ga (Japanese Patent Laid-Open No. 2002-115940), tin -Indium-bismuth alloy, when the composition ratio is Sn: Xwt%, In: Ywt%, Bi: Zwt%, X + Y + Z = 100 and 4 ≦ X ≦ 10, 56 ≦ Y ≦ 63, a low-temperature melting alloy for fusible plugs (Japanese Patent Laid-Open No. 2001-214985), and a fusible alloy composed of bismuth, indium and tin (Japanese Patent Laid-Open No. 2003-130240). is there.
JP 2002-115940 A JP 2001-214985 A JP 2003-130240 A

  A fusible stopper used as a safety device for a refrigeration apparatus has been made of a solder alloy containing Pb and Cd which are harmful substances. However, in recent years, there has been an active movement to protect the global environment, and there is a tendency to eliminate harmful components from parts used in equipment such as refrigeration equipment. In particular, Cd and Pb components are regulated because they adversely affect the human body. As an alloy for fusible plugs that does not contain harmful components such as Cd and Pb, a tin (Sn) -indium (In) -bismuth (Bi) -based alloy is disclosed as in Patent Document 1 described above. The alloy for fusible stoppers has poor creep characteristics at low temperatures, and the alloy may be pushed out by pressure over time during use as a safety device for refrigeration equipment. After a certain period of time, the refrigeration equipment is stopped. The fusible stopper had to be replaced.

  In addition, as in Patent Document 3, in the case where metal fine particles are added to a soluble alloy made of bismuth, indium, and tin, the metal fine particles dispersed on average in the alloy composition are subjected to high temperature and high pressure for a long time. In the meantime, since the same composition gradually becomes unevenly distributed, there is a drawback that the creep characteristics are likely to be lowered.

  Although it is not an alloy for fusible plugs of a refrigeration apparatus, it contains 34 wt% or more and 63 wt% or less of bismuth and 1 wt% or more and 24 wt% or less of tin, and the balance is an indium alloy for temperature fuse ) Is disclosed. Since thermal fuses are used as a load for countermeasures against abnormally high temperatures in electronic equipment, it is only necessary to shut off electricity depending on the temperature, and pressure is not applied during use, and mechanical strength such as creep characteristics of the alloy is taken into consideration. Therefore, it cannot be used as a soluble plug alloy.

The present inventors do not contain harmful components such as Cd and Pb, and even when used for a long time as a safety device of a refrigeration apparatus, the alloy is not extruded from the fusible stopper, such as creep characteristics, mechanical The object is to provide a highly soluble fusible stopper.

  As a result of intensive studies on the drawbacks of conventional alloys having a solid phase temperature and a peak temperature at 65 to 75 ° C., the present inventors have found that in a Bi—In—Sn based alloy, an alloy having a limited composition range is present. It was found that it has a solid phase temperature and a peak temperature at about 66 to 70 ° C., and its temperature range is very narrow and suitable for an alloy for fusible stoppers, thereby completing the present invention. Moreover, the alloy does not contain any harmful components such as Cd and Pb.

  The alloy that melts at 66 to 70 ° C. according to the present invention is an alloy for fusible plugs characterized by consisting of Sn 5 to 8 mass%, Bi 31 to 34 mass%, Sb 0.2 to 4 mass%, and the balance In. .

  The soluble stopper alloy of the present invention does not contain any harmful components such as Cd and Pb, and the alloy is not pushed out from the soluble stopper. It can be used for a long time without replacing.

The fusible plug depends on the melting temperature of the fusible plug alloy. However, since the pressure from the refrigerator is always applied, if the mechanical strength such as creep characteristics is weak, it cannot be used as a safety device. .
In a Bi-In-Sb-Sn alloy, which is an alloy having a solid phase / peak temperature at about 66 to 70 ° C. according to the present invention, if the amount of Sn is less than 5 mass%, the mechanical strength of the alloy itself is low, so the pressure resistance test There is a disadvantage that the amount of popping out of the alloy exceeds a predetermined amount. If the amount of Sn exceeds 8% by mass, the solid phase temperature of the Bi-In-Sb-Sn alloy decreases, so the melting temperature of the alloy Near the temperature range to be used, the strength of the alloy deteriorates and the creep characteristics in the operating temperature range deteriorate. Therefore, in the Bi—In—Sb—Sn alloy of the present invention, the Sn content must be 5 to 8% by mass. If the Bi content is less than 31% by mass, the liquid phase temperature of the Bi-In-Sb-Sn alloy will rise too much and the meltability of the alloy will deteriorate, failing to pass the melting test, and the amount of Bi will be 34% by mass. If the amount is larger, the eutectic point of the Sn—In alloy is removed, so that the liquidus temperature rises too much and the meltability of the alloy becomes worse and the melting test is not passed. Furthermore, the alloy having a solid phase / peak temperature at about 66 to 70 ° C. according to the present invention further includes Sb added to the Bi—In—Sn alloy. This is because a solvent having a high solidification pressure such as R404A is used for a refrigerator in which an alloy having a solid phase / peak temperature at about 66 to 70 ° C. is used, so an alloy having higher pressure resistance is required. is there. In the present invention, by adding Sb, it is possible to maintain sufficient pressure resistance even when using R404A which is a solvent having a high coagulation pressure. If the amount of Sb of the Bi-In-Sb-Sn alloy of the present invention is less than 0.2% by mass, the mechanical strength of the alloy itself is low, so there is a drawback that the pop-out of the alloy in the pressure resistance test exceeds a predetermined amount. If the amount of Sb exceeds 4% by mass, the solid-phase temperature of the Bi-In-Sb-Sn alloy decreases, so the melting temperature of the alloy approaches the temperature range in which it is used, and the strength of the alloy deteriorates. Occurs and degrades the creep characteristics in the operating temperature range. Therefore, the Bi—In—Sb—Sn alloy of the present invention must have an Sb content of 0.2 to 4 mass%. In the present invention, an alloy for soluble plugs having a strong creep characteristic in an operating temperature range of 66 to 70 ° C. is obtained by using Sn 5 to 8 mass%, Bi 31 to 34 mass%, Sb 0.2 to 4 mass%, and the balance In. It becomes possible to obtain. Further, it should be desired to use an alloy of Sn 5% by mass, Bi 33% by mass, Sb 2% by mass and the balance In, so that a soluble plug alloy having a narrow operating temperature range and strong creep characteristics can be obtained. When Sn, Bi, and Sb, which are the basic constituent components of the fusible plug alloy of the present invention, deviate from the above composition range, the melting temperature range becomes wide and the operation stability is impaired.

  Further, in the Bi—In—Sb—Sn alloy of the present invention, a strength additive element can be added. Examples of the strength additive element include Cu, Ge, Ag, Au, Zn, Ni, and La group. The La group is also called a lanthanoid and is an element having characteristics similar to La of La and Ce, Pr, Nd, Pm, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu. These strength-added elements can be effective singly or in combination. In the Bi—In—Sb—Sn alloy of the present invention, especially the addition of Cu as a strength additive element most improves the creep characteristics. However, unlike the invention of Patent Document 3 described above, these strength-added elements are always used after being melted into a Bi—In—Sb—Sn alloy, so that if the added amount is excessively increased, the melting temperature of the alloy is increased. End up. Therefore, the total amount of strength-added elements is desirably 2.0% by mass or less. The most preferable addition amounts of each strength addition element are Cu 0.1 to 1.0 mass%, Ge 0.1 to 1.0 mass%, Ag 0.1 to 0.7 mass%, Au 0.1 to 0.6 mass%, Zn 0.2 to 0.6 mass%. , Ni 0.02 to 0.1% by mass, La group 0.01 to 0.1% by mass, and if the amount is less than this, the effect of improving the strength of the alloy does not appear. Will not work in the specified temperature range.

  The fusible stopper of the present invention is obtained by melting a Bi-In-Sb-Sn alloy and sealing it in a blank material. From the shape of the blank material, a single screw type, a double screw type, a flare tube type, a porous type, etc. It is applicable to the soluble stoppers.

The soluble stopper alloy and the soluble stopper of the present invention are prepared and their characteristics are compared.
The soluble alloy shown in Table 1 was prepared, and the heating curve by differential thermal analysis of each alloy composition was measured. The end point of the endothermic peak, the lowest end point of the endothermic peak, and the end point of the endothermic peak were determined. The liquidus temperature was measured. Table 1 shows the melting temperature of each alloy.
In Table 1, Comparative Examples 3 and 5 are alloys for fusible plugs of Patent Document 2.
Melting temperature measurement conditions are as follows.
1. Differential thermal analysis measurement / differential thermal analysis measuring device SII differential scanning calorimeter / heating rate: 5deg / min
・ Sample weight: 10 mg

Next, the meltable stopper alloy shown in FIG. 1 is filled into the single screw type soluble stopper blank 1 shown in FIG. 1 to make a soluble stopper, and creep characteristics for each alloy composition (referred to as pressure resistance test). ), And the operating temperature of the fusible stopper. For the pressure test and the operation test, a fusible stopper having a total length of 28 mm and an inner diameter of the tip of 3 mm was used.

2. Pressure test
1.) A fusible stopper filled with the Bi-In-Sb-Sn alloy of the present invention is placed in a thermostatic chamber set at 65 ° C. , connected to a compressor, and a pressure of 12.5 MPa is applied.
2.) After 24 hours, remove the fusible plug from the temperature-controlled room and disconnect from the compressor.
3.) After standing for 24 hours, measure the length of the filled soluble alloy that has escaped from the blank.
4.) Table 1 shows the length of the alloy stretched during the pressure resistance test, and FIG. 2 shows a representative photograph of the alloy compositions of the examples and comparative examples in Table 1 measured at 65 ° C. In the photograph, 1 is the result of the soluble stopper of Example 4, and 2 is the result of the soluble stopper of Comparative Example 5.

3. Operating temperature
1.) Connect the fusible plug to the compressor and apply a pressure of 3 MPa.
2.) Put the fusible stopper connected to the compressor into the tank and heat the water in the tank.
3.) Measure the temperature at which air has escaped from the fusible stopper in the tank as the operating temperature.

  As can be seen from the photograph in FIG. 2, the fusible plug 2 of the comparative example has a lower solid phase temperature than the fusible plug of the example, so that the fusible plug alloy is pulled out and extended. In particular, the fusible plug 2 of Comparative Example 5 was a semi-molten body by heating at 65 ° C. under the test conditions. On the other hand, in the fusible plug 1 of the embodiment of the present invention, the fusible plug alloy is not easily pulled out and the fusible plug is not extended.

  The fusible plug of the present invention operates at about 66 to 70 ° C., and the fusible plug alloy has good low-temperature creep characteristics, so that the fusible plug alloy does not come out of the blank material even when pressure is applied for a long time at a high temperature. Therefore, when used in a protective device for a refrigeration apparatus, the conventional soluble stopper that can be used for a long time has an effect.

Cross section of fusible stopper Photograph of fusible stopper extruded by pressure after pressure test

Explanation of symbols

1 Blank material 2 Fusible plug alloy 3 Screw

The fusible plug alloy of the present invention can be used not only as a fusible plug used for a protection device of a refrigeration apparatus, but also as an alloy for a sprinkler that is constantly subjected to pressure, like the fusible plug.

Claims (3)

An alloy for fusible plugs having an operating temperature of 66 to 70 ° C, comprising an alloy of Sn 5 to 8 mass%, Bi 31 to 34 mass%, Sb 0.2 to 4 mass%, and the balance In. To the fusible plug alloy, Cu 0.1 to 1.0% by mass, Ge 0.1 to 1.0% by mass, Ag 0.1 to 0.7% by mass, Au 0.1 to 0.6% by mass, Zn0 .2 to 0.6% by mass, Ni 0.02 to 0.1% by mass, La group 0.01 to 0.1% by mass of at least one element added at a minimum of 2.0% by mass or less The alloy for fusible plugs according to claim 1, wherein the operating temperature is 66 to 70 ° C. A fusible plug having an operating temperature of 66 to 70 ° C. using the fusible plug alloy according to claim 1.